Arie Zeichner

Collection Efficiency of Gunshot Residue (GSR) Particles from Hair and Hands Using Double-Side Adhesive Tape

Experiments were carried out to sample GSR particles (GSRs) from hair using double-side adhesive coated aluminum stubs (the tape-lift method). Although it was claimed in the literature that double-side adhesive tape is not suitable for sampling GSRs from hair, we have not encountered problems with this method. In laboratory experiments it was possible to find GSRs even 24 h after shooting if the hair had not been washed. No significant difference in collection efficiency was found between this technique and the more complicated method of swabbing the hair using a comb with a solvent-damped cloth (the swabbing-and-comb method). It was found that 200 to 300 dabbings are necessary to achieve maximum collection efficiency from hair with the double-side adhesive. As assessed subjectively, it was noted that stickiness is lost after about 100 dabbings. This method has been used in casework in Israel for about a year and a half and, in some cases, GSRs were found in samples from hair but not in samples from hands. We have also studied collection efficiency from hands of the double-side adhesive. It was found that 50 to 100 dabbings are necessary to achieve maximum collection efficiency, while stickiness appeared lost after about 20 to 30 dabbings. No substantial danger of skin debris concealing GSRs was observed.

Gunshot Residue Particles Formed by Using Different Types of Ammunition in the Same Firearm

Examples of some exceptional compositions of gunshot residue particles, formed by using different types of ammunition in the same firearm, are presented. The composition that may be encountered in casework may differ appreciably from the “classic” criteria for identification of gunshot residues. This fact must therefore be taken into account by the expert when interpreting case results, and thus, every case has to be dealt with on an individual basis.

Improved method for shooting distance estimation. Part 1. Bullet holes in clothing items

An improved method for firing distance estimation on clothing is described. The novel part of the method includes transfer of total nitrite (nitrite ions and smokeless powder residues) from the target to an adhesive lifter. After the transfer, lead and copper deposits around the bullet entrance hole are visualized by rhodizonate and rubeanic acid, respectively. The Modified Greiss Test is carried out after alkaline hydrolysis of the smokeless powder residues on the adhesive lifter.

A novel method for extraction and analysis of gunpowder residues on double-side adhesive coated stubs

A study was conducted to develop an efficient method for extraction and analysis of gunpowder (propellant) residues from double-side adhesive coated stubs, which are used for sampling suspects or their clothing for gunshot (primer) residues (GSR). Conductive and non-conductive double-side adhesives were examined, and the analysis was carried out by gas chromatography/thermal energy analyzer (GC/TEA) and ion mobility spectrometry (IMS). The optimal procedure for the extraction, as was developed in the present study, employs two stages: (1) extraction of the stubs with a mixture of 80% v/v aqueous solution of 0.1% w/v of sodium azide and 20% v/v of ethanol employing sonication at 80 degrees C for 15 min. and (2) residues from the obtained extract were further extracted with methylene chloride. The methylene chloride phase was concentrated by evaporation prior to analysis. Extraction efficiencies of 30-90% for nitroglycerine (NG) and for 2,4-dinitro toluene (2,4-DNT) were found. No significant interferences in the analysis were observed from the adhesives or skin. Interferences were observed in the analysis by the GC/TEA of the samples collected from hair. The method enables analysis of propellant residues on a double-side adhesive coated stub after it was examined for primer residues by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX). Thus, the probative value of the evidence may be increased.

Concentration Techniques for the Detection of Gunshot Residues by Scanning Electron Microscopy/Energy Dispersive X-Ray Analysis (SEM/EDX)

The efficiency of the filtration process for concentrating small populations of gunshot residue (GSR) particles (for detection by scanning electron microscopy/energy dispersive X-ray analysis [SEM/EDX]) was examined with a novel method using GSR particle suspensions. Methods of concentrating and segregating GSR particles on small areas (for example, 7 mm2) using both filtration and heavy liquid separations with centrifugation were examined from the practical point of view. It is shown that, in real cases, there may be an intrinsic difficulty in concentrating GSR particles as a result of a pile up of extraneous material or clogging of the collecting filter or both. Collection of GSR particles from clothes using a suction method was compared to the direct glue-lift technique. The suction method involved trapping the GSRs in an organic solvent and recovering them on a membrane filter. The method proved less efficient than using the glue-lift technique. From the findings in this study, it seems that the most efficient way of detecting GSR particles by SEM/EDX is by using the recently developed automated systems directly on glue-lift samples without any pretreatment.

Gunshot Residue Particles Formed by Using Ammunitions That Have Mercury Fulminate Based Primers

Ammunition having mercury fulminate-based primers are commonly manufactured by Eastern Bloc countries and used extensively in the Middle East. Gunshot residue (GSR) particles formed by firing these types of ammunition were examined. It was observed that much lower percentage of mercury-containing GSR particles were found in samples taken from a shooter as compared to the percentage of such particles in samples from cartridge cases. This fact must therefore be taken into account when interpreting case results. A plausible explanation for the results described is proposed.

More on the Uniqueness of Gunshot Residue (GSR) Particles

The question of “accepted uniqueness” of several types of GSR particles is discussed. Based on our experience, we propose to include GSR particles formed in firing the Sellier Bellot, Prague (SBP) ammunition in the group of “unique” GSR particles. With the advent of autosearch systems for GSR analysis in crime labs, a better statistical basis for the extent of uniqueness of various types of GSR particles may be achieved.

Some Special Observations Regarding Visible Transmission Spectra of Inks and an Improved Method for Their Discrimination by Microspectrophotometry

Various blue and black inks are shown to change their transmission spectra by applying pressure and smearing them as deposits on glass slides. A similar phenomenon is observed with deposits of copper phthalocyanine tetrasulfonic acid tetra sodium salt. It is shown that transmission spectra of small samples of inked paper fibers smeared (crushed) on glass slides resemble spectra of smeared ink deposits and are more reproducible than spectra of inked fibers in a mounting medium. This advantage is especially significant in the case of examining ink traces on tinted paper.

Recent Developments in the Methods of Estimating Shooting Distance

A review of developments during the past 10 years in the methods of estimating shooting distance is provided. This review discusses the examination of clothing targets, cadavers, and exhibits that cannot be processed in the laboratory. The methods include visual/microscopic examinations, color tests, and instrumental analysis of the gunshot residue deposits around the bullet entrance holes. The review does not cover shooting distance estimation from shotguns that fired pellet loads.

Improved Method for Shooting Distance Determination. Part 2—Bullet Holes in Objects that Cannot be Processed in the Laboratory

An improved method for firing distance determination on exhibits that cannot be processed in the laboratory such as cars, doors, windows, or furniture is described. The novel part of the method includes transfer of total nitrite (nitrite ions and smokeless powder residues) from the target to an adhesive lifter. After the transfer, vaporous lead and copper deposits around the bullet entrance hole are visualized on the target by sodium rhodizonate and rubeanic acid, respectively. The Modified Griess Test is carried out after alkaline hydrolysis of the smokeless powder residues on the adhesive lifter.